Take-up fastener for resisting uplift loads in light framed construction

ABSTRACT

A take-up fastener is disclosed for fastening a level in a frame construction to the level below so as to resist upward forces generated by wind and other sources on the framed construction. The take-up fastener in general includes a take-up plate, or washer, fastened to a portion of the upper level and a take-up screw fit through the take-up plate and fastened to the adjacent level below. Once the take-up fastener is fully assembled, the take-up plate includes a pair of tabs which are capable of engaging threads on a take-up screw in a way that allows one-way motion of the take-up screw relative to the take-up plate. In particular, the take-up plate can move downward relative to the take-up screw, for example on constricting of the wooden members to which the take-up plate is affixed. However, the engagement between the take-up plate and take-up screw prevents movement of the take-up plate upward with respect to the take-up screw, for example upon an upward load due to wind or other external force.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 12/409,255, entitled “TAKE-UP FASTENER FOR RESISTING UPLIFTLOADS IN LIGHT FRAMED CONSTRUCTION,” filed Mar. 23, 2009, whichapplication is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fastener for opposing uplift forcesin light framed construction.

2. Description of the Related Art

In construction such as residences, small buildings, multi-family andother light-framed construction, an uplift restraint system typicallyincludes uplift resisting connectors at the roof to top of a wall, topof a wall to vertical studs, vertical studs between adjacent floors andto the foundation. Winds and other external forces may generate upwardloads on framing members. In order to counteract these upward loads, theframing members may be anchored to the surface on which they aresupported. On the ground level, anchor rods are typically sunk into aconcrete foundation, and the bottom plate of the wall is bolted to theanchor rods. For levels built on top of the first level, straps areoften used to anchor the upper level to the level below. FIG. 1 is aperspective view of an upper level 30 anchored to a lower level 20 via acoil strap 40 in a light framed construction. While only one anchorstrap is shown affixed to a pair of aligned studs 22 and 32 on theadjoining levels, coil straps may be provided in each pair of alignedstuds in the respective levels to anchor the level 30 to the level 20.

Prior art FIG. 1 shows a stud 22 and top plates 24 and 26 from lowerlevel 20. A stud 32, bottom plate 34, subflooring 36 and floor joist 38are shown from upper level 30. Nails or other fasteners may be providedalong the length of coil strap 40 (at least in the portions overlappingthe lower stud 22 and upper stud 32) to fasten the coil strap 40 to theupper and lower levels. A typical coil strap 40 may be formed of variousthicknesses including 16 gauge steel, such as for example the CS16 coilstrap by Simpson Strong-Tie Company, Inc. of Pleasanton, Calif.

While effective at anchoring upper levels to lower levels, coil strapshave certain drawbacks. First, they need to be positioned on theexterior of a framed construction, and require scaffolding or othersupport mechanisms to allow workers to install the coil straps. Second,the vertical studs must align on adjacent floors for strapping to beinstalled. Third, the wooden members in a framed construction, includingthe top and bottom plates, floor and rim joists, settle or compressduring to the load of the structure and shrink over time. Shrinkage inlumber occurs as the moisture in the wood members evaporates causing themembers to constrict. This constriction may result in buckling or bowingoutward of the strap, as well as any siding or exterior covering of theframed construction.

SUMMARY OF THE INVENTION

The present invention, roughly described, relates to a take-up fastenerfor fastening a level in a frame construction to the level below so asto resist upward forces generated by wind and other sources on theframed construction. The take-up fastener in general includes a take-upplate, or washer, fastened to a portion of the upper level and a take-upscrew fit through the take-up plate and fastened to the adjacent levelbelow. Once the take-up fastener is fully assembled, the take-up plateincludes a pair of tabs which are capable of engaging threads on atake-up screw in a way that allows one-way motion of the take-up screwrelative to the take-up plate. In particular, the take-up plate can movedownward relative to the take-up screw, for example on constricting ofthe wooden members to which the take-up plate is affixed. However, theengagement between the take-up plate and take-up screw prevents movementof the take-up plate upward with respect to the take-up screw, forexample upon an upward load due to wind or other external force.

The take-up plate includes a pair of tabs facing each other and angledupward off of the flat planar surface of the take-up plate. A hole istapped in between the tabs so that the tabs have semicircular edgeswhich are threaded to a diameter and pitch to match correspondingthreads on the take-up screw. Once the hole is tapped into the tabs ofthe take-up plate, the tabs are bent further upward to an assembly angleso that the take-up screw may be assembled through the opening betweenthe tabs without binding against the tabs.

The take-up screw in general includes a head portion separated from ashank portion by a circular flange. Threads for engaging the tabs,referred to herein as tab engagement threads, are provided adjacent tothe flange but slightly spaced therefrom by a clearance space. Theopposite end of the shank includes cutting threads for driving into andsecurely fastening within a lower level.

On assembly, the take-up screw may be inserted through the openingbetween the pair of tabs and driven into and through portions of theupper level, such as for example through a bottom plate and subflooring.The distal end of the screw is then further inserted and driven intoportions of the lower level, such as for example the top plates. Whenthe take-up screw is nearly fully inserted, the tabs engage the flangebeneath the head of the take-up screw. Further insertion of the screwthen causes the flange to permanently deform the tabs downward, tothereby decrease the diameter of the hole defined between the tabs.

This is the finished assembly position. Thereafter, owing toconstriction of wooden members, the take-up plate may slide down alongthe shank of the take-up screw. As the tabs are deformed, if the platehas moved far enough down relative to the screw, the tabs engage withthe tab engagement threads on the screw. Thereafter, continued downwardmovement of the plate relative to the screw is permitted, for exampleupon further constriction of the wooden members. However, once the tabsengage with the tab engagement threads on the screw, the tabs preventupward movement of the plate relative to the screw, for example under anupward load exerted on the upper level by wind or other external forces.As the upward force of the take-up plate and tabs increases against thetake-up screw, the tabs bind more tightly against the tab engagementthreads of the take-up screw.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of adjacent levels in a frame constructionaffixed together using a conventional coil strap.

FIG. 2 is a perspective view of adjacent levels affixed together usingtake-up fasteners according to an embodiment of the present invention.

FIG. 3 is a top view of a take-up plate according to an embodiment ofthe present invention and FIG. 3A is a cross sectional view through line3A-3A in FIG. 3.

FIG. 4 is a top view of the take-up plate of FIG. 3 during a first stageof fabrication.

FIG. 5 is a top view of the take-up plate of FIG. 3 during a secondstage of fabrication.

FIG. 6 is a top view of the take-up plate of FIG. 3 during a third stageof fabrication.

FIG. 7 is a top view of a take-up screw according to an embodiment ofthe present invention.

FIG. 8 is a side view of a take-up plate and take-up screw during afirst stage of assembly of the take-up fastener according to anembodiment of the present invention.

FIG. 9 is a side view of a take-up plate and take-up screw during asecond stage of assembly of the take-up fastener according to anembodiment of the present invention.

FIG. 10 is a side view of a take-up plate and take-up screw during athird stage of assembly of the take-up fastener according to anembodiment of the present invention.

FIG. 11 is an enlarged partial view of the take-up plate and take-upscrew shown in FIG. 10.

FIG. 12 is an enlarged partial view of the take-up plate and take-upscrew in a fully assembled position.

FIG. 13 shows a relative position of the take-up plate and take-up screwafter wooden members of the framed construction have constricted due toevaporation of moisture within the wooden members.

FIG. 14 is a take-up fastener according to a first alternativeembodiment of the present invention.

FIGS. 15-18 are views of a take-up fastener according to a secondalternative embodiment of the present invention.

FIG. 19 is a view of a take-up fastener according to a third alternativeembodiment of the present invention.

FIGS. 20 and 21 are views of a take-up fastener according to a fourthembodiment of the present invention.

DETAILED DESCRIPTION

The present invention will now be described with reference to FIGS.2-21, which in embodiments relate to a take-up fastener for receivingupward loads in levels of a framed construction. It is understood thatthe present invention may be embodied in many different forms and shouldnot be construed as being limited to the embodiments set forth herein;rather these embodiments are provided so that this disclosure will bethorough and complete and will fully convey the invention to thoseskilled in the art. Indeed, the invention is intended to coveralternatives, modifications and equivalents of these embodiments, whichare included within the scope and spirit of the invention as defined bythe appended claims. Furthermore, in the following detailed descriptionof the present invention, numerous specific details are set forth inorder to provide a thorough understanding of the present invention.However, it will be clear to those of ordinary skill in the art that thepresent invention may be practiced without such specific details.

FIG. 2 is a partial perspective view of adjacent levels 102 and 104 of aframed construction. Level 102 is fastened to level 104 by take-upfasteners 100 which effectively transfer upward loads from level 102 tolevel 104, while allowing for settling of wooden members in the framingof the respective levels as explained in greater detail hereinafter.FIG. 2 shows a portion of the first and second levels including threestuds 106 in level 102 and three studs 108 in level 104. There will bemany more studs 106 and 108 in the respective layers. In addition tostuds 106, the elements in level 102 shown in the partial view of FIG. 2also include bottom plate 110, connectors 112 for connecting studs 106to bottom plate 110, subflooring 114, and a floor joist 116. In additionto studs 108, the elements in level 104 shown in the partial view ofFIG. 2 also include top plates 120 and 122, and connectors 124 forconnecting studs 108 to top plates 120 and 122.

A take-up fastener 100 according to the present invention may beprovided between each pair of adjacent studs 106, 108. However, it isunderstood that the take-up fastener 100 may be provided between lessthan all adjacent pairs of studs, and more than one take-up fastener maybe provided between an adjacent pair of studs, in further embodiments ofthe present system. Moreover, it is understood that the take-up fastenermay be used with framing members other than studs in furtherembodiments, such as for example a Strong-Wall shearwall of SimpsonStrong-Tie Company, Inc., Pleasanton, Calif.

As seen in FIG. 1, take-up fastener 100 includes a take-up plate, orwasher, 140 affixed to base plate 110 of level 102, and a take-up screw160. Take-up screw 160 has a first end affixed to plate 140 and a secondend extending down into and fastened within top plates 122 and 120 oflevel 104. Each of these elements is explained in greater detail below.

Take-up plate 140 will now be described in greater detail with respectto FIGS. 3-6. FIG. 3 shows a top view of a finished take-up plate 140.Take-up plate 140 includes a pair of tabs 142 and 144 which angle upwardout of a plane of the otherwise flat take-up plate 140. The tabs 142 and144 are tapped with a threaded bit, so that the tabs 142, 144 eachinclude semi-circular notched edges. The semi-circular notched edgesdefine part of a circular hole 148 matching the diameter of threads onthe take-up screw 160 as explained hereinafter. The notched edges aretapped with threads having a pitch matching the thread pitch of thethreads on the take-up screw as explained hereinafter.

Take-up plate 140 is formed with a pair of grooves 150 at the base wherethe tabs 142, 144 bend upward from take-up plate 140. The grooves 150allow the tabs 142, 144 to deform elastically a small amount asexplained hereinafter. Grooves 150 may be cut or stamped into thesurface of take-up plate 140 to a depth of 0.0075 inches deep, thoughthis depth may be greater or lesser in alternative embodiments. Take-upplate 140 may be formed of 10 gauge steel with a length of 3% inches anda width of 3 inches. It is understood that the gauge, length and widthof take-up plate 140 may vary in alternative embodiments. Moreover, itis understood that plate 140 may be shapes other than rectangular orsquare in further embodiments. In one embodiment, the corners of plate140 may be omitted or removed so that the plate is generally circular,oblong or oval. In such embodiments, the plate could be sized so that itfits within the width of the bottom plate 110 regardless of itsorientation when fastened to the plate.

Take-up plate 140 further includes fastening holes 148 near the outerperiphery of plate 140. The fastening holes are provided to receivenails, screws, bolts or other fasteners for fastening the take-up plate140 to the bottom plate 110. While the plate 140 is affixed to bottomplate 110 in embodiments, the bottom plate 110 may be affixed to otherportions of level 102 in further embodiments.

Formation of take-up plate 140 will now be explained with reference toFIGS. 4-6. Plate 140 may be formed in a die which allows fastening holes148 to be cut along with longitudinal slits 152 and a transverse slit154 centered and extending between slits 152. The longitudinal andtransverse slits 152, 154 define tabs 142, 144. Longitudinal slits 152may be centered along the length of plate 140 and may have a length ofapproximately 1.12 inches so that each tab has a length of 0.56 inches.The longitudinal slits 152 may be spaced from each other the distanceequal to the length of transverse slit 154 which may for example be 1inch. It is understood that each of the above-described dimensions mayvary up or down in further embodiments of the present invention.

Referring now to the end views of FIGS. 5 and 6, grooves 150 may beformed in the plate 140 at the base of the tabs 142, 144. The tabs maybe bent upward to an angle, referred to herein as an engagement angle,which in embodiments may be 33.75°. The engagement angle may be greateror lesser than this in alternative embodiments. Bent at the engagementangle, the tabs 142, 144 may extend a distance of 0.3125 inches abovethe surface of take-up plate 140. Once bent to the engagement angle, thetabs are tapped to define the hole 146 seen for example in FIG. 3. Thetabs may be tapped for example with a ⅜ inch bit having 24 threads perinch. As mentioned above and explained hereinafter, this diameter andthread pitch matches the diameter and thread pitch of tab engagementthreads formed on take-up screw 160. FIG. 3A is a cross-sectional viewthrough FIG. 3 showing threaded hole 146 on tab 142. Tab 144 may havesimilar threads.

After hole 146 is tapped between tabs 142 and 144, the tabs 142 and 144are bent further upward to a larger angle, referred to herein as theassembly angle, which may for example be 42°. At such an angle, hole 146has a diameter of approximately 0.4 inches. It is understood that theassembly angle may be greater or lesser than 42° with the limitationthat the diameter of hole 146 when tabs are bent in the assembly angleis greater than the outer diameter of all threads along the shank oftake-up screw 160.

The take-up screw 160 will now be explained with reference to FIG. 7.Screw 160 is an elongate cylindrical member including a head 162 and ashank 164. Head 162 may for example be a hex head, though other knownconfigurations for head 162 may be used in alternative embodiments. Head162 is separated from shank 164 by an annular flange 166 having agreater diameter than shank 164. In embodiments, the flange 166 may havea diameter of 0.8 inches, though it may be larger or smaller than thatin further embodiments.

Shank 164 includes three sets of threads or annular rings along itslength. A first set of threads are the tab engagement threads 168 whichinteract with tabs 142 and 144 in the fully assembled take-up fastenerto allow one-way motion of take-up screw 160 relative to take-up plate140 as explained below. Tab engagement threads 168 may have an outerdiameter of ⅜ inches and a thread pitch of 24 threads per inch. Tabengagement threads 168 may extend approximately one inch along the shank164, though this distance may be lesser or greater in furtherembodiments. A clearance space 170 may be provided between tabengagement threads 168 and flange 166. As explained hereinafter, theclearance space 170 allows the tabs 142 and 144 to deform downwardwithout binding against the shank 164.

Shank 164 may further include annular rings 172 provided approximatelyfive inches down from flange 166, though they may be closer or fartherfrom the flange 166 in further embodiments. As explained hereinafter,annular rings 172 have a diameter at least as large as tab engagementthreads 168 so that the annular rings bore a hole through bottom plate110 and subflooring 114 having a large enough diameter so that the tabengagement threads do not bind within bottom plate 110 or subflooring114.

Cutting threads 176 are provided at the distal end of shank 164. Cuttingthreads 176 may have a ⅜ inch diameter and may have a length of 4.5inches. It is understood that the diameter and length of cutting threads176 may vary in alternative embodiments. Threads 176 may be of the typefound on the Strong-Drive® screw from Simpson Strong-Tie Company, Inc.,Pleasanton, Calif. As shown in FIG. 2 and as explained in greater detailhereinafter with respect to FIG. 10, cutting threads 176 are driven intoand held fast within top plates 120 and 122 of level 104 to fasten thetake-up fastener 100 to level 104. The distal end of take-up screw 160may include a cutting tip so that take-up screw 160 may be driventhrough bottom plate 110, subflooring 114, and top plates 120 and 122without having to initially create a bore hole through those members. Aninitial bore hole may be drilled in alternative embodiments.

The assembly of take-up fastener 100 will now be explained withreference to FIGS. 8-12. FIG. 8 shows take-up screw being driven throughbottom plate 110 and subflooring 114 (partially shown in FIGS. 8-12).Tabs 142 and 144 of take-up plate 140 are bent to the assembly angle asexplained above so that all portions of take-up screw 160 may passthrough hole 146 defined by tabs 142 and 144. Thus, all portions ofshank 164 including cutting threads 176, annular rings 172 and tabengagement threads 168 may pass through the hole 146 between tabs 142and 144 without any portions of the shank 164 contacting either of tabs142 and 144.

In the position shown in FIG. 8, cutting threads 176 have cut a borehole through bottom plate 110 and subflooring 114. The diameter of thishole is increased by annular rings 172, which are shown just passinginto bottom plate 110 in FIG. 8. In particular, instead of augering intothe members 110 and 114, the annular rings enlarge the bore hole to adiameter at least equal to the outer diameter of the tab engagementthreads 168. Thus, the tab engagement threads 168 may be drawn into thebore hole without binding, as shown for example in FIG. 9. As analternative to annular rings, reverse cutting threads may be providedthat have a reverse orientation to the cutting threads 176.

In FIG. 10, take-up screw 160 has been driven through bottom plate 110and subflooring 114 to the point where tabs 142 and 144 of plate 140first contact flange 166. In this position, cutting threads 176 areembedded within top plates 122 and/or 120. FIG. 11 is an enlargedpartial view showing the fastener 100 shown in FIG. 10, with the tabs142 and 144 abutting against flange 166 of take-up screw 160. FIG. 12 isan enlarged view similar to FIG. 11, with the take-up screw 160 havingbeen driven further into members 110 and 114. As the take-up screw isdriven from the position in FIG. 13 to the position in FIG. 14, theflange 166 bears against tabs 142 and 144 and permanently deforms thetabs 142 and 144 downward toward each other so that the diameter of hole146 between the tabs decreases. As indicated above, clearance space 170is provided adjacent to flange 166 to prevent binding of the tabs 142,144 against the take-up screw 160 as the tabs are deformed and thediameter of hole 146 grows smaller.

FIG. 12 shows the finished assembly of take-up fastener 100. Flange 166has deformed tabs 142 and 144 downward toward each other so that tabs142 and 144 are permanently deformed back to the engagement angle ofFIG. 5. This was the angle at which hole 146 was tapped through tabs 142and 144. While deforming the tabs 142, 144 back down to the initialengagement angle ensures good engagement of the threaded tabs withthreads 168 as explained below, it is understood that the finalengagement angle shown in FIG. 12 may be different than the initialengagement angle shown in FIG. 5.

As explained in the Background of the Invention, wooden members mayconstrict after assembly due to the evaporation of moisture. Forexample, in FIG. 13, the thickness of bottom plate 110, floor and rimjoist 116 and top plates has shrunk, and plate 140 affixed thereto ispulled down along the shank of the stationary take-up screw 160. In theembodiment shown in FIG. 13, the thickness of members 110, 114 hasshrunk to the point where tabs 142 and 144 engage tab engagement threads168. As indicated above, the hole tapped between tabs 142 and 144 has adiameter and thread pitch matching the diameter and thread pitch of tabengagement threads 168. However, as tabs 142 and 144 are bent slightlyupward and have a slight degree of elasticity owing to grooves 150, tabs142 and 144 are able to flex slightly to allow take-up plate 140 toslide down along the length of tab engagement threads 168.

However, in the event of an upward load on level 102, the fastener 100prevents upward movement of plate 140 and members 110, 114 affixedthereto, relative to take-up screw 160. In particular, the tappedthreaded edges of tabs 142 and 144 engage within the tab engagementthreads 168. An upward force of take-up plate 140 relative to thetake-up screw 160 results in a downward force of the engagement threads168 against the threaded edges of tabs 142, 144, thus resisting theupward movement of the take-up plate 140, members 110 and 114, and level102 in general. Larger upward forces only increases the force with whichtabs 142 and 144 grip tab engagement threads 168.

In this manner, the take-up fastener 100 allows one-way motion of thetake-up plate 140 relative to take-up screw 160. This one-way motionallows the wooden members 110 and 114 to constrict and slide down alongthe length of take-up screw 160 but prevents upward movement of themembers 110 and 114 upon an upward force exerted on level 102. Moreover,as take-up fastener 100 is provided on the interior of level 102,fastener 100 may be inserted without the need of scaffolding or othersupport structures on the exterior as is otherwise necessary to installconventional coil straps. In embodiments, take-up fasteners 100 may beused to affix second and subsequent levels to the below-adjacent level.

The gauge of take-up plate 140 is selected so that tabs 142, 144 havemore than one thread for engaging more than one thread from tabengagement threads 168. For example, at 24 threads per inch, tabs 142,144 may have a thickness sufficient to be tapped with between 3 and 4threads along the edges of tabs 142, 144 defining the hole 146. Thus,upon settling of the members 110, 114 so that tabs 142 and 144 engagetab engagement threads 168, tabs 142 and 144 may have a plurality ofthreads which engage with tab engagement threads 168. It is understoodthat different gauge steels may be used for take-up plate 140, and thenumber of threads which engage between tabs 142, 144 and tab engagementthreads 168 may be less than 3 and more than 4 in further embodiments.

FIG. 14 shows a portion of a take-up fastener 200 according to analternative embodiment of the present invention. The embodiment of FIG.14 includes a take-up plate 240 which may be identical to take-up plate140 described above. However, in the embodiment of FIG. 14, take-upscrew 160 may be replaced with a take-up bolt 260. In this embodiment, abore may be formed through the bottom plate 110 and subflooring 114 oflevel 102 as well as the top plates 120 and 122 of level 104.Thereafter, an elongate cylindrical bolt 260 having a diameter smallerthan the bore hole may be inserted through the bore hole. The plate 240may then be screwed down over the tab engagement threads 268 formed inthe top of bolt 260. In the embodiment of FIG. 14, the tabs 242 and 244may be deformed to the engagement angle, shown in FIGS. 5 and 12, of forexample 33.75°.

The diameter and thread pitch on the edges of tabs 242, 244 may be thesame as the diameter and thread pitch of the engagement threads 268.Thus, the plate 240 can screw down over the bolt 260 with the tabs 242and 244 engaging with tab engagement threads 268. Once plate 240 isscrewed down over take-up bolt 260, a nut may be affixed over theopposite end of bolt 260 protruding through top plates 120 and 122. Inthe embodiment of FIG. 14, the plate 240 may have a size and shape sothat the plate 240 at its widest diameter still fits within the width oftop plate 110. In this way, plate 240 may be screwed down over bolt 260to a final position of any orientation and no portion of plate 240 willextend beyond the width of bottom plate 110.

A take-up fastener according to a further embodiment is shown in FIGS.15-19. The embodiment of FIGS. 15-19 begins with a bearing plate 300.Tab sections 302 and 304 (shown by dashed lines in FIG. 15) arepartially cut and bent inward so the ends of tabs 302 and 304 meet at acenter of bearing plate 300 as shown in FIG. 16. In FIG. 17, a threadedhole 308 is tapped through the ends of tabs 302 and 304 and through acenter of bearing plate 300. Bearing plate 300 may be affixed to bottomplate 110 via fastening holes (not shown) as described above.

The embodiment of FIGS. 15-19 may work with a take-up screw 360 whichmay be identical to take-up screw 160 described above. Initially, tappedhole 308 may have a diameter larger than the diameter of the shank oftake-up screw 360. However, when a flange 368 of take-up screw 360engages the tabs 302 and 304, the tabs 302 and 304 are deformed throughthe central tapped hole in bearing plate 300 so as to decrease the sizeof the tapped hole between tabs 302 and 304. Thus, as shown in FIG. 18,this configuration allows one-way motion of the bearing plate 300relative to the take-up screw 360. However, if upward forces attempt tomove the bearing plate upward relative to the take-up screw, tabs 302and 304 are pulled into the central bore hole and bind against tabengagement threads 368 to prevent upward movement of bottom plate 110and subflooring 114 as described above. FIG. 19 may be identical to theembodiment of FIGS. 15-18 with the exception that bore 308 throughbearing plate 300 may be larger so that both portions of tabs 302 and304 as well as a portion of the bearing plate 300 itself are drawn downinto the bore created by take-up screw 360.

FIGS. 20 and 21 show a further embodiment of a take-up fastener 100according to the present invention. As seen in the exploded view of FIG.20, this embodiment may include a take-up screw 460 which may beidentical to take-up screw 160 described above. This embodiment furtherincludes a housing 402, a cap 404, and a threaded wedge 406. Threadedwedge 406 may be formed of two independent halves which define acylindrical threaded bore when the halves are brought together. Thehalves may be held together by being inserted into elastic cap 404. Thisembodiment further includes a bearing plate 410 which affixes to bottomplate 110 in a manner similar to take-up plate 140 described above.Bearing plate 410 includes a tapered opening 412 with a diameter largeenough to receive a bottom portion 414 of wedge 406.

As seen in FIG. 21, when assembled, take-up screw 460 may be insertedthrough enclosure 402, cap 404 and between the halves of wedge 406 downthrough opening 412 in bearing plate 410. When assembled, wedge 406allows upward motion of the take-up screw 460 relative to bearing plate410. However, upon an upward force on bearing plate 410 relative totake-up screw 460, wedge 406 is forced down further into tapered opening412, thereby forcing the halves of wedge 406 to grip take-up screw 460more tightly to thereby prevent upward movement of bearing plate 410relative to take-up screw 460.

Although the invention has been described in detail herein, it should beunderstood that the invention is not limited to the embodiments hereindisclosed. Various changes, substitutions and modifications may be madethereto by those skilled in the art without departing from the spirit orscope of the invention as described and defined by the appended claims.

What is claimed is:
 1. A method of fastening an upper level to a lowerlevel below the upper level, the method resisting upwards loads on theupper level, the method comprising the steps of: (a) inserting anelongate cylindrical member through a hole in a portion of the upperlevel, the elongate cylindrical member having a proximal end and adistal end opposite the proximal end; (b) fastening the proximal end ofthe elongate cylindrical member to a portion of the lower level; (c)positioning the distal end of the elongate cylindrical member within theportion of the upper level defining the hole of said step (a) in amanner that allows downward movement of the portion of the upper levelrelative to the elongate cylindrical member, but prevents upwardmovement of the portion of the upper level relative to the elongatecylindrical member; wherein the portion of the upper level defining thehole comprises a plate having a air of tabs bent upward toward eachother from the slate the hole being defined between the tabs, the methodfurther comprising the step of deforming the tabs from a first angle insaid step (a) where the elongate cylindrical member is inserted throughthe hole between the tabs, to a second angle where the tabs are capableof engaging threads on the elongate cylindrical member.
 2. The method ofclaim 1, further comprising the step of edges of the tabs grippingthreads on the elongate cylindrical member, said step of edges of thetabs gripping threads on the elongate cylindrical member allowingdownward movement of the plate relative to the elongate cylindricalmember, but preventing upward movement of the plate relative to theelongate cylindrical member.
 3. The method of claim 1, the elongatecylindrical member having threads near the distal end, the tabs capableof engaging the threads when bent in the second angle to allow the tabsto slide down the threads of the elongate cylindrical member, whilepreventing upward movement of the tabs relative to the threads.
 4. Amethod of fastening an upper level to a lower level below the upperlevel, the method resisting upwards loads on the upper level, the methodcomprising the steps of: (a) inserting an elongate cylindrical memberthrough a plate in a portion of the upper level, the elongatecylindrical member having a proximal end and a distal end opposite theproximal end, and the plate including a pair of tabs through which thedistal end of the cylindrical member is received, the pair of tabsincluding tabs bent relative to a plane of the plate, said step (a)comprising the step of deforming the tabs from a first angle where theelongate cylindrical member is inserted through the hole between thetabs, to a second angle where the tabs are capable of engaging threadson the elongate cylindrical member, the pair of tabs allowing movementof the elongate cylindrical member in a first direction relative to theplate, and resisting movement of the elongate cylindrical member in asecond direction opposite the first direction; and (b) fastening theproximal end of the elongate cylindrical member to a portion of thelower level.
 5. The method of claim 4, said step (a) comprising the stepof edges of the tabs gripping threads on the elongate cylindricalmember, said gripping step allowing movement of the elongate cylindricalmember relative to the plate in the first direction, but preventingmovement of the elongate cylindrical member relative to the plate in thesecond direction.
 6. The method of claim 4, the elongate cylindricalmember having threads near the distal end, the tabs capable of engagingthe threads when bent in the second angle to allow the tabs to slidedown the threads of the elongate cylindrical member, while preventingupward movement of the tabs relative to the threads.
 7. A method offastening an upper level to a lower level below the upper level, themethod resisting upwards loads on the upper level, the method comprisingthe steps of: (a) inserting an elongate screw through a plate in aportion of the upper level, the elongate screw having a proximal end anda distal end opposite the proximal end, and the plate including a pairof tabs threaded to receive threads in the distal end of the screw, thepair of tabs including tabs bent relative to a plane of the plate, saidstep (a) comprising the step of deforming the tabs from a first anglewhere the elongate screw is inserted through the hole between the tabs,to a second angle where the tabs are capable of engaging threads on theelongate screw, the pair of tabs allowing movement of the elongate screwin a first direction relative to the plate, and resisting movement ofthe elongate screw in a second direction opposite the first direction;and (b) fastening the proximal end of the elongate screw to a portion ofthe lower level.
 8. The method of claim 7, said step a comprising thestep of edges of the tabs gripping threads on the elongate screw, saidgripping step allowing movement of the elongate screw relative to theplate in the first direction, but preventing movement of the elongatescrew relative to the plate in the second direction.
 9. The method ofclaim 7, the elongate screw having threads near the distal end, the tabscapable of engaging the threads when bent in the second angle to allowthe tabs to slide down the threads of the elongate screw, whilepreventing upward movement of the tabs relative to the threads.